1. Field of the Invention
The present invention relates to an improved method for measuring, determining, recording and correlating event-related electrical brain potentials ("ERP") with the use of whole skull electroencephalography, to a novel disposable electrode cap, to a novel computer system arrangement and more particularly to a method of measuring and determining a large number of meaningful brain electrical potential changes in response to a continuously presented and varied specific verbal stimulus or verbal stimuli interspersed with non-significant verbal stimuli comprising known truths or true statements and false statements concerning the subject to establish an actuarial or historical personal base line for use within a predetermined time period and analyzing the measured ERP responses against the personal base line established from the related ERP data established from known stimuli to determine the probable truth or falsity of either a non-verbal (e.g. manual) response or verbal response to at least one specific stimulus in the form of a verbal query within the predetermined time period, using a computer.
2. Description of the Prior Art
The history of lie detection by psychophysiological methods has been fraught with problems of flawed human judgment, unreliability and frequent invalidity.
Medical records from the Hindus dated 900 B.C. were the first to note the use of blushing (facial vasodilation) in the detection of guilt. The earliest most impressive use was in the case of Eristratus, physician to Alexander the Great, who determined by use of the "tumultuous rhythm" of the heart that the crown prince of the Seleucid court in Syria was guilty of sexual relationship with his recently obtained stepmother. Months later, a female was born. Hugo Munsterberg in a published work dated 1908 was the first well known psychologist to give approval to the technique developed by one of his students, who reported a 96% accuracy rate using blood pressure as the single measure.
There have been two main techniques in the lie detection problem. The relevant/irrelevant technique ("RIT") asks subjects questions related to the crime and neutral questions that refer to everyday events. The problem with this approach is that if one is asked about a murder, it is not uncommon to achieve a greater physiological reactivity just to the question, which is irrelevant to the guilt of the subject.
To improve the RIT method, in 1947 Reid developed the control question technique ("CQT"). In this technique the control question is constructed to have greater emotional impact than the relevant question. Thus the subject might be asked "Did you ever do anything you were ashamed of?" Backster reported in a 1962 publication that he developed a quantification of this method by having the examiner rate each physiological measure on a scale of 1-3 for the control/relevant questions, depending upon the relative magnitudes of the responses to the questions. Thus, degrees of how much a subject falls in the respective category can be established.
Dr. D. Raskin et al. later developed computerized scoring for the CQT, taking it out of the hands of human judgment. Some approaches to the CQT employ a "truth control" test or "the guilt complex test" during which the subject is questioned regarding an additional crime. The questions are formulated the same and the underlying assumption by the subject that he is a suspect for both crimes must be met for this method to be effective and valid, which poses a special problem for the police in the beginning of an investigation.
This last approach was developed by Lykken in 1960. It is called the guilty knowledge test or concealed information test (herein after "GKT"). In this approach indirect questions are posed to the subject which are directed towards information that only the guilty subject would know. For example, "Was she wearing a black dress that night?" A multiple choice format has been employed in this approach. For example, "Was she wearing a red dress that night?" By focusing on several aspects of the crime and repetition of the questioning, false positives can be avoided. The use of the GKT has been supported in the published research on the subject. In Japan, the use of the GKT is the preferred technique, but it has not been widely used in the U.S.
In reviewing the results of published research in this area, noteworthy is a work by Ben-Shakhar in 1990 which reported that the studies employing the CQT resulted in average correct classification of guilty subjects between 80% and 84% in simulated and field studies, respectively. Among innocent subjects, the correct classification was 63%-72%, respectively. The GKT, on the other hand, averaged across 10 studies a 84% hit rate for the guilty subjects and 94% hit rate for those simulating innocence.
Published works by Gustafson and Orne in 1965 demonstrated that by asking the subjects to respond "no" to all the questions they were able to obtain a higher identification rate than the control group which were instructed to respond with a free association. A third group was instructed not to respond. The researchers were able to obtain significantly higher than chance hit rates for this silent group and "no" group. Further research published by Horneman and O'Gorman in 1985 and by Elaad and Ben-Shakhar in 1989 has validated this effect of silence during the question period.
Additional published research by Cutrow et al. (1972) and also previously indicated by Thackray and Orne (1968) validated the use of several measures in increasing accuracy of prediction. They found that although galvanic skin response ("GSR") was the single best predictor, the combined score using six measures produced more effective results. The novel invention accurately and effectively extends this discovery a thousandfold and combines it with certain other novel procedures to substantially improve results.
Electroencephalography ("EEG") is a method of recording brain waves of an individual which are generated by the action potentials of neurons residing in the cortex of the brain. In today's standard 1020 systems, 19 electrodes are positioned on the scalp covering the skull with conductive paste while two other electrodes are attached to a person's ears as reference points. The paste has several drawbacks. Sometimes, conduction is poor, intermittent, or impaired.
Spectral analysis of these brain waves is performed when each electrical potential signal is displayed versus a unit of time as representative of a particular brain wave detected by an electrode. Each brain wave from each electrode is amplified in voltage the same percentage. The wavelengths or frequencies in each brain wave are measured and then a signal uniquely representing each frequency of the brain wave is sent to a computer for sorting of the different frequencies of which the signal is composed. The range as measured in Hertz (cycles per second) is defined by the computer and analyzed in terms of absolute microvolts of electrical potential, relative potentials, coherence values (the similarity of the signal between two points on the scalp), ratio symmetry (the relationship between two points in terms of a particular bandwidth), peak amplitude (the peak microvolts of a particular bandwidth), peak frequency (the highest frequency of a particular bandwidth), and phase (the time lag difference between the signals at two different points on the scalp).
An epoch is the time it takes the computer to record a measurement of all of the signals from each of the electrodes. The sampling rate of the computer is the number of times it records measurements from the electrodes each second. Thus, the sampling rate of the computer determines the length of each epoch. For example, if the sampling rate is set at 128, then the maximum hertz range one is able to analyze is the sampling rate divided by 4, i.e., 32 hertz. Hertz is defined as the number of waves per second emanating from an electrode. If the sampling rate is set at 512, then one is able to analyze frequencies up to the 128 Hertz range. Different Hertz ranges have been associated with different mental states. For example, the alpha range of 8 to 12 or 13 Hertz has been associated with a relaxed state of mind. The Beta band of 12 or 13 to 128 has been associated with the working, problem solving brain.
Simultaneous video and EEG recording has been employed to assess for faking of seizures, etc. and for other pathology determinations.
An electroencephalograph ("EEG") is a device which measures and records brain wave activity by sensing spontaneous electrical potential of a person's scalp, cortex, or cerebrum at various sites. Each EEG channel corresponds to a particular electrode combination attached to the patient. The sensed EEG potential at each channel is amplified by a differential amplifier, and amplifier output signal is typically used to control movement of the recording pen of a polygraph. The EEG record is a long strip of polygraph paper containing a wave form for each EEG channel. The polygraph paper is driven at a predetermined rate (e.g., 30 millimeters per second) and is marked to represent predetermined time increments.
EEG signals exhibit different frequencies depending upon varying activity. The EEG signal frequencies are classified into four basic frequency bands, which generally referred to as "Delta" (0 to 4 Hertz); "Theta" (4 to less than a 8 Hertz); "Alpha" (8-13 Hertz); "Beta" (greater than 13 Hertz). One determines the predominant frequency of a particular channel during a particular time period by measuring the period of the EEG signal wave form shown on EEG record. The EEG signal wave form typically includes multiple frequency components. EEG outputs can be driven by specific extrinsic or endogenous events. For example, a regularly occurring stimulus will elicit a series of waves each time it is presented. The entire series is referred to as an event-related potential (ERP).
Besides the frequency of the EEG or ERP wave forms, the amplitude is measured. Significance has been established when large amplitudes of brain waves occur at about 300 ms or more after the eliciting event. There is evidence to suggest that this P300 wave process is invoked when the updating, or "refreshing", representations in working memory is required. Donchin, Psychophysiology. Vol. 18, 493-513 (1981); Fabiani, Karis, and Donchin, Psychophysiology, Vol. 22, 588-589 (1981).
Large P300's are elicited by rare or unexpected events, when they are relevant to the task the subject is performing. Such events may lead to restructuring or updating of working memory, and this activity is part of the ongoing process of maintaining accurate schemas of the environment. The updating process may lead to an "activation" of the representation, or to the "marking" of some attribute of the event that was crucial in determining the updating process. This restructuring of the representation of an event is assumed to facilitate the subsequent recall of the event, by providing valuable retrieval cues, so that the greater the restructuring that follows an individual event, the higher the probability of later recalling that event. If P300 amplitude represents the degree of restructuring in working memory, then P300 amplitude should also predict later recall. Fabriani, Karis and Donchin, Psychophysiology, Vol. 23, 298-308 (1986).
In view of the current knowledge of the frequency and amplitude of brain wave forms and with the advent of widespread use of the computer in behavioral neuroscience, the analysis of data has become easier. Oftentimes, it is desirable to have an objective method of determining whether or not a person has seen or otherwise has knowledge of a particular item, such as a weapon, a crime scene configuration, a secret document, a stolen object, or another person's face. Such knowledge is what is taught by prior art procedures and devices used in guilty knowledge tests, a sub-category of procedures used in physiological detection of deception ("lie detection").
The present invention is directed to a reliable, valid easy-to-use and accurate procedure for determining guilty or other knowledge on the part of an individual whose simple verbal report may be unreliable for various reasons. If a discreet stimulus, for example, a sound, a light flash, a tap-is presented to a human, his electroencephalogram shows a series of time-locked responses called event related potentials (ERP).
It was shown in the 1960's that if a subject is presented with a series of stimuli of two types, e.g., a high tone and a low tone, and if either of those tones is presented in 20 of 100 trials (with the remaining 80 trials containing the other tone), the rare stimulus will evoke a large ERP retorted to as "P3" or the previously described P300 brain wave. In this so-called "oddball" paradigm, it is known that P3 amplitude varies with rarity. Sutton, S. et al., Science. 150, 1187-1188, (1965).
in the 1970's and thereafter, other workers reported that P3 is evoked by words (or pictures) previously seen by a subject when presented in a word (or picture) series which also includes novel words (or pictures) which fail to evoke P3. Karis, D. et al., Cognitive Psychology, vol. 16, 177-216; Neville, H. et al., Proc. Nat Ac. Sci. U.S.A., vol. 79, 2121-2123, (1982).
The present invention also relates to a novel method which utilizes both the aforementioned effects so that one can tell by objective ERP inspection alone which of the presented stimuli has previously been seen by the subject or loaded into the subject's neural memory. The invention further relates to an apparatus which provides means for a repeated presentation of the significant stimulus and means for analyzing the ERP responses to determine the significance of all gathered responses. The prior art only used P3 responses in an "odd-ball" procedure with simple auditory stimuli, e.g. high tones and low tones, that were presented singly to subjects and whatever tone was presented less often evoked a P3 response. Pritchard, et al., Psychophysiology, Vol. 23, No. 2, 166-172 (1986).
The prior art also utilizes the "odd-ball" paradigm in which the stimuli is a simple visual flash differing in brightness. Johnson, Jr. Annuals of the N.Y. Acad. of Sci. Vol. 425, pages 223-230 (1984). Like Pritchard, other studies utilized P3 responses relating them to memory updating processes, expectancy processes, surprise, and so forth. None of the prior art articles disclose the odd-ball procedure with repeated, meaningful word stimuli in the context to be utilized to detect guilty knowledge or other recognition processes.
In the paper by Fabiani, et al. Psychophysiology, Vol. 23, pp. 298-308 (1986) and Neville, et al. supra, verbal, meaningful stimuli is used in a variant kind of "odd-ball", paradigm bearing on recognition memory. However, this teaching differs greatly from the present invention. Three or the most notable aspects are as follows: (a) These studies were not and could not be configured as field-relevant deception detection paradigms, because both novel and previously seen words (or pictures) in these studies were never repeated within the EEG run; (b) the average ERP to previously seen words (or pictures) was an average of responses to a series of all different words (or pictures); and (c) the average ERP to novel words (or picture) was likewise an average of responses to all different novel words (or pictures). This kind of paradigm is specifically unsuited to the real criminal-type lie detection investigations to which this invention is directed since it is usually a single item (the murder weapon, the stolen item, the classified document) which is involved in a real crime.
The Fabiani and Neville, reports are directed at and tailored to scientific elucidation of memory processes. In these studies, the repetition of words is avoided for fear of engaging habituation processes which would tend to reduce P3 effects. In the present invention, the "odd-ball" item is "odd ball" by virtue of its familiarity (e.g., as guilty knowledge). The stimuli are all meaningful words, and they are presented in the simplest possible, basic "odd-ball" design. There are other studies in the literature which do not use quasi verbal stimuli which are repeatedly presented. A review of the literature reveals that these studies are not using "odd-ball" paradigms, and are, in fact, studying memory processes with extremely complicated procedures tailored to these purposes: For example, Gomer et al., Physio. Psych, Vol. 4 (1) pp. 61-65 1976), (1976 Ford, et al., Elect. Clin. Neuroph. 47:450-459 (1979 Kramer et al. Psychophysiology, Vol. 23 No. 1, 33-47 (1986) and Adam and Collins, Elec. Clin. Neurol. 44: 147-156 (1978), all use a "go-no go" or pattern matching paradigms. A set of letters or numbers is memorized and then the subject is given a trial series in which he decides whether ("go") or not ("no go") a memorized target stimulus is presented.
The present invention requires but one series of trials; others use several sets. The present invention requires no feed-back whereas the prior an methods do. The prior an methods use warning tones whereas the present invention does not. It is notable that typically the prior art reports P3 responses to both target and non-target stimuli. Although target effects are often reported to be bigger, unambiguous use of P3 responses in field investigations of deception requires the kind of virtually all-or-none results that are seen in the present invention. Further, the prior art studies use simple stimuli, digits or letters, rather than meaningful words.
The main intent of most prior art methods was elucidation of memory retrieval processes. These methods focused on P3 latency rather than on amplitude. Instruments have been used to determine psychological stress, for example, the apparatus described in U.S. Pat. No. 2,944,542 relates to a blood pressure measuring device that indicates variations in the velocity of pulse wave thereby indicating a change in emotional state. U.S. Pat. No. 3,971,034 describes a method and apparatus for identifying psychological stress by converting oral impulses into electrical signals and recording, observing and analyzing those signals.
U.S. Pat. No. 3,893,450 relates to method and apparatus for examining brain wave form by providing stimuli such as light and determining the characteristic of a mathematically determinable point in the brain wave forms of the subject. U.S. Pat. No. 4,188,956 relates to a method of acquiring and compressing neurometric test data by means of a digital computer system. U.S. Pat. No. 4,579,125 relates to a method for processing analog EEG signals to provide an indication of cerebral activity. None of the teachings of the references, however, have been used for the combination of a method to determine P3 responses from repeatedly presented stimulus interspersed with no significant stimuli to obtain results directed towards detection and control question testing.
More recently, U.S. Pat. No. 4,932,416 issued on Jun. 12, 1990 to Rosenfeld for a method for recording and analyzing event-related potentials (ERP), and their respective P300 brain wave responses from a repeatedly presented guilty knowledge or control question stimulus interspersed with non-significant stimuli. A computer is utilized to interpret and analyze the responses for guilty knowledge relating these responses to the responses to control questions. An improvement was patented by Rosenfeld in U.S. Pat. No. 5,137,027 on Aug. 11, 1992 wherein the ERP's concurrently generated by a repeated paradigm are encephalographically sensed and analyzed for P3 content and the P3 waves generated and compared via computer. Based on selected criteria, a conclusion regarding actual prior act performance is made. Computer means are utilized to regulate the paradigm presentation and to interpret and analyze the P3 responses.